Replace a 2.5 with a 4.0 ... or other suggestions ....

[SteveTheFolkie]

I just mounted 31's on my YJ and it's kinda pathetic on uphills - figure the 4.0 would bring a bit of life back to the old girl - how much of a PIA would it be to swap in a 4.0?  I assume the same transmission and t-case - is it just a matter of wiring harness (firewall forward), motor mounts and the motor itself?  I've done swaps before BUT they were all pre-fuel injection / computerized ignition (although living in Adams County I could probably swap in a 1966 Chevy 327 without anyone paying attention) -

Failing that - suggestions for gearing?  Would swapping in the 5SPD diff ratios help out?  I don't pile on the miles so fuel mileage isn't that big a deal -

Thanks - and cheers!

Steve

[hillbilly]

no no no not a good or even close idea nothing matches at all the trans are diff so youll have to change that too ,the 2.5 has a 21 spline tcase a 4.0 has a23,the radiator,fuel lines cat comp sensors and all the goodies a buddy of mine did it and had about $4-5,000 in it and thats just the swap.a v-8 -carb swap w trans and tcase and driveshafts and then with that big of a jump you gotta get bigger axles too been there wasnt cheap but just a heads up on what your in for.      almost cheaper to sell it and buy one with a 4.0 in it.imo

[chasm]

Steve:
Keep your 4 banger and look at some other ways to get more HP! I have the 2.5 5-speed in the 93 YJ with 31's and it does just fine on the highway and more especially, off-road. A flow-through type exhaust system will help get you a little more power. I didn't believe it at first and then I tore up the stock exhaust at Rausch Creek and had it replaced with a stainless flow through and the difference was noticeable!
Some folks are switching to K&N and similar style intakes for increased performance. Between the exhaust and intake, you can get some of your power back without a lot of hassle or a lot of bucks.

When I go up to 33" tires, I'm going to regear. that will cost about 1200 bucks to do it right. I'm keeping the 4 banger as long as I can. She tells me when she is maxed out and I don't have to worry about breaking axles or twisting shafts because I used too much skinny pedal with an engine like a 4.0!

Come to Rausch Creek with me sometime. I'd love to run with another 4 banger YJ on 31's! 

[SteveTheFolkie]

Thanks for the caveats and suggestions - sounds like, if I really wanted to go the 4.0 route it'd be a whole lot easier and cheaper to re-jeep myself - but that's not gonna happen so it looks like I'll be sticking with the 2.5 and figuring out how to add a bit of oomph to the old girl -

Steve